The TSX stock exchange defines an index as a statistical measure of the state of the stock market, based on the performance of certain stocks. The performance of the index is typically viewed as a broad indicator of the direction of the economy. Originally known as the TSE 300 the composite index was created in 1977, with a base level of 1000 as of 1975. Through the years the index consisted of a sample of 300 companies, though the companies that comprised the index varied from year to year. Stocks were dropped when they no longer met exchange requirements for size and liquidity.
Effective May 1st, 2002 the index has been managed by Standard & Poor's Corp. of New York. The name was changed from the TSE 300 to the S&P/TSX Composite Index. Along with the S&P branding came new rules. Tougher criteria for meeting size and liquidity standards were imposed and there is now no fixed number of companies in the index. Since May 2002 the number of companies has dropped from 300 to 212 as of November of 2003.